London -LRB- CNN -RRB- -- After three marathons , I really should know what to do by now . There is simply no substitute for plenty of training when running a marathon . But this Sunday I will be pounding the streets of my hometown Brighton , southern England , having done almost no preparation . So how will I fare ?

Ideally a marathon runner should be doing 40 to 50 miles a week for at least three or four months before race day . The training is intensely boring , but it conditions every part of the body -- including the mind -- for the pummeling that 26.2 miles exerts on it . My knees , shins , Achilles and hamstrings hurt the most as the miles mount , and they can only get stronger and more resilient through practice .

I used to dismiss as a myth the notion of the `` wall , '' the pain barrier that marathon runners experience at about 20 miles . This happens when energy reserves are depleted , forcing the body to start burning fat . It can leave you feeling nauseous -- again , training helps to condition the body to running long distances . However , I hit the wall in both my last two races , and I 'm terrified it will happen again this Sunday .

Before my previous well-prepared marathons I ran respectable times of about three hours and 30 minutes . This year though , just like the excuses I used to give for failing to do my homework at school , I simply have n't had time to do enough practice runs .

The only real distances under my belt are the three miles that I walk each day from Victoria Station in London up to CNN 's bureau in Soho . An intense workload at both the office and home mean I rarely have time to spend the one or two hours on top of this that I should be doing .

So in a desperate effort to get race-fit , I have been trying to pack about four months of training into just two or three weeks . But three demanding children and a house restoration project mean the only time I 've had to run is late at night . This means I 've been trudging along Brighton 's seafront , running the gauntlet of its colorful nightlife , such as night-clubbers , stag and hen nights and assorted other lost souls .

I 've heard several other runners recently talking smugly about tapering down in the final stages of marathon preparation . I 'm still tapering up . Last night I ran 17 miles and felt shattered . I hope I feel better for this Sunday 's race . I do n't know if I 'll last the distance but I intend to find out . Follow my last-minute preparations here . Next week I 'll tell you how it went .

A week later ...

Well , it seems I was fitter than I feared ! After worrying that I had n't done nearly enough training for Sunday 's Brighton marathon , I finished in a creditable three hours and 35 minutes -- only a couple of minutes slower than last year 's time .

Most of my longer runs were done in the fortnight before the race -- contradicting the usual advice that you train for three or four months , then ease off , or taper , in the last 10 days or so .

Still , I must have been doing something right , as I felt reasonably comfortable for most of the race . It only really became an ordeal for the last two or three miles , when my legs and feet felt like concrete and my chest started to tighten .

I was helped on my way -- as ever during a marathon -- by the thousands of spectators lining the route . Many of them handed me jelly baby sweets , which provided a welcome lift as I neared the finish . The weather was perfect for running : sunny but fresh , and I in fact enjoyed , yes enjoyed , the whole day .

I felt pretty rough straight after the race , but better than last year when I was sick after I crossed the line . But I managed to keep walking -- always the best strategy , and walked the mile back to my home where I lay on the sofa all afternoon . I managed to hobble about the house , but I got my children to be my slaves for the day .

I did n't sleep very well on Sunday night because my legs were tingling so much . On Monday I went to work in London and my legs were more stiff but not painful , but I managed to walk three miles . It was a bit of a struggle getting in and out of my chair but by Tuesday the stiffness had pretty much gone , and now I ca n't tell I ran 26 miles four days ago . I even ran the 1.5 miles from Victoria Station to the CNN bureau in Soho this morning in 15 minutes .

I can only conclude that the exercise I take during the rest of the year is sufficient to keep me fit enough to run a marathon . Who knows : maybe training is all a myth ! It certainly saved me a lot of time -- I always find the worst thing about preparing for a marathon is the monotony of running mile after boring mile for months beforehand

So I would implore anyone considering a marathon to get out and give it a go : it 's really not as hard as you might think . Sure , 26.2 miles -LRB- 42 kilometers -RRB- is a long way , but as long as you have a decent level of fitness , you 'll be able to run a fairly fast marathon . You never know , you might even enjoy it !

@highlight

Peter Wilkinson is CNN 's Senior Digital Producer

@highlight

He is a veteran of the London and Brighton marathons

@highlight

The marathon covers a distance of 26.2 miles -LRB- 42km -RRB-